Three-dimensional Ni(OH)2 nanoflakes/graphene/nickel foam electrode with high rate capability for supercapacitor applications

Supercapacitor, known as an important energy storage device, is also a critical component for next generation of hydrogen fuel cell vehicles. In this study, we report a novel route for synthesis of three-dimensional Ni(OH)₂/graphene/nickel foam electrode by electrochemical depositing Ni(OH)₂ nanoflakes on graphene network grown on nickel foam current collector and explore its applications in supercapacitors. The resulting binder-free Ni(OH)₂/graphene/nickel foam electrode exhibits excellent supercapacitor performance with a specific capacitance of 2161 F/g at a current density of 3 A/g. Even as the current density reaches up to 60 A/g, it still remains a high capacitance of 1520 F/g, which is much higher than that of Ni(OH)₂/nickel foam electrode. The enhanced rate capability performance of Ni(OH)₂/graphene/nickel foam electrode is closely related to the presence of highly conductive graphene layer on nickel foam, which can remarkably boost the charge-transfer process at electrolyte–electrode interface. The three-dimensional graphene/nickel foam substrate also significantly improves the electrochemical cycling stability of the electrodeposited Ni(OH)₂ film because of the strong adhesion between graphene film and electrodeposited Ni(OH)₂ nanoflakes. Results of this study provide an alternative pathway to improve the rate capability and cycling stability of Ni(OH)₂ nanostructure electrode and offer a great promise for its applications in supercapacitors.     

Surfactant-assisted synthesis and catalytic activity for SOx abatement of high-surface-area CuMgAlCe mixed oxides

CuMgAlCe mixed oxides were prepared by a modified coprecipitation–calcination method using CTAB as surfactant template. All the precursors showed hydrotalcite-like layered structure and mixed oxides with mainly periclase phase were obtained after calcination. Catalytic activity for SO₂ removal of mixed oxides was examined through adsorption–reduction cycles under the conditions similar to those of FCC units. The results showed that incorporation of both Ce and Cu could improve SO_x oxidative chemisorption. CTAB/metal molar ratio during synthesis had a significant influence on the structural properties of mixed oxides. Sample CuMgAlCe-0.1 prepared by CTAB/metal molar ratio of 0.1 had the highest specific area 142.2 m²/g and also presented the best SO₂ adsorption rate and capacity. This behavior is mainly due to its exposed more adsorption sites provided by high specific surface area, facilitating SO₂ diffusion and contact with active components. It still possessed excellent cyclic stability that is beneficial for industrial application.     

A study on tension behavior considering thermal effects in roll-to-roll E-printing

The mathematical model for tension in a moving web by Shin [1] was extended by considering thermal strain due to temperature fluctuations in the drying of a roll-to-roll system. The extended model describes variations in tension and includes terms that represent the change of the Young’s Modulus, the thermal coefficient, and the thermal strain. In this paper, a new control scheme based on the extended model is proposed for mitigation of tension disturbances due to thermal strain in the drying process. Tension feedback control logic generally is not be applied due to the fact that register errors can be induced by speed alterations that help to compensate for tension disturbances. But in our approach, the thermal strain in the web is compensated for by means of velocity adjustments without adding extra register errors in the steady state. A computer simulation followed by an experimental validation was carried out to confirm the performance of the proposed method. The results show that the proposed model is useful for describing tension behavior and suggest that tension control logic improves control precision for the drying module of a roll-to-roll e-printing system.     

A correlation study on the phenolic profiles and corrosion inhibition properties of mangrove tannins (Rhizophora apiculata) as affected by extraction solvents

The objective of this study was to investigate the correlation of phenolic compositions and corrosion inhibition properties of Rhizophora apiculata bark extracts as affected by nine solvent systems. Several phenolic compositions, namely, total phenolic content (TPC), total flavonoid content (TFC), condensed tannin content (CTC) were investigated. In addition, the inhibitive actions of tannin extracts on mild steel in 1 M HCl solution were studied by potentiodynamic polarization and electrochemical impedance spectroscopy. The results showed that extraction solvents had significant effects on TPC, TFC, CTC and inhibition properties of extracts. A correlation between CTC and inhibition properties of R. apiculata bark extracts was revealed.     

Photopolymerization of hyperbranched aliphatic acrylated poly(amide ester). I. Synthesis and properties

The hyperbranched aliphatic poly(amide ester) (HAPAE) was synthesized based on 4‐N,N‐di(2‐hydroxy ethyl)‐4‐ketobutyric acid prepared by the reaction of succinic anhydride with diethanol amine, as an AB₂ monomer (repeating unit), and with 2‐ethyl‐2‐(hydroxymethyl)‐1,3‐propanediol, as a core molecule, using acid catalysis. The second generation of the product was characterized by measuring dynamic viscosity, which decreased sharply with the increase in frequency. The product exhibits relative thermal stability as analyzed by thermogravimetry in a nitrogen atmosphere. The glass transition temperature, determined by differential scanning calorimetry, is ?27 °C. The molar mass was measured by vapor pressure osmometry. The polydispersity, measured by size exclusion chromatography, is 2.16. Dynamic mechanical thermal analyses were performed to characterize the thermal properties of the ultraviolet‐cured films of the acrylate‐modified HAPAE. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1630–1636, 2001     

Upper bounds on the symbol-error probability of MPSK with phase error using pawula F-function IV

This letter presents an alternative derivation of the Case IV of Pawula F-function and an approximation for the corresponding probability density function (pdf) in the presence of the Tikhonov distributed phase error. The pdf of Case IV is used to obtain new upper bounds for the conditional and average symbol-error probabilities of M-ary phase shift keying with phase error over additive white Gaussian noise channels. Numerical results demonstrate the validity of the upper bounds.     

Directed electrochemical synthesis of ZnO/PDMcT core/shell nanorod arrays with enhanced photoelectrochemical properties

In this paper, we demonstrate a simple two-step electrochemical deposition strategy for synthesizing ZnO/Poly(2,5-dimercapto-1,3,4-thiadiazole) (PDMcT) core/shell nanorod arrays. The as-synthesized ZnO/PDMcT samples are characterized by Fourier-transform infrared (FTIR), Raman spectroscopy, power X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The ZnO/PDMcT nanorod arrays are found to exhibit significantly enhanced photocurrent density in photoelectrochemical cell applications as compared to the prinstine ZnO nanorod arrays.     

Measurements of fuel mixture fraction oscillations of a turbulent jet non-premixed flame

This work describes new type of combustion instability for which the 3-way coupling between mixing, flame heat release, and acoustics is modified by local buoyancy effects. Measurements of fuel mixture fraction are made for a non-premixed jet flame in a combustion chamber to assess the dynamics of mixing under imposed acoustic oscillations (22-55 Hz). Infrared laser absorption and phase resolved acetone-planar laser induced fluorescence are used to measure the fuel mixture fraction and then the degree of fuel/air mixing is calculated by determining the unmixedness. Results show acoustic excitation causes oscillations in the degree of fuel/air mixing at the driving frequency, which results in oscillatory flame behavior. This oscillatory flame behavior couples to the buoyancy and this in turn affects the mixing. Results also show that the mixing becomes less effective when the excitation frequency is increased or when the flame is present, compared to the non-reacting case. This work describes a key coupling mechanism that occurs when buoyancy is a significant factor in the flow field.     

A Heuristic Approach to the Railroad Track Maintenance Scheduling Problem

Abstract: Every year, billions of dollars are spent on rail track maintenance to keep the serviceability of the railroad network. These maintenance projects (of different types) must be performed by suitable maintenance teams within a planning horizon. This article presents a time‐space network model to solve the track maintenance scheduling problem (TMSP). The objective is to minimize the total travel costs of the maintenance teams as well as the impact of maintenance projects on railroad operation, which are formulated by three types of side constraints: mutually exclusive, time window, and precedence constraints. An iterative heuristic solution approach is proposed to solve the large‐scale TMSP model with a large number of side constraints. The proposed model and solution approach are applied to a large‐scale real‐world problem. Compared to the current industry practice the model outcome eliminated all hard side‐constraint violations and reduced the total objective value (travel costs and soft side‐constraint violation penalties) by 66.8%.